Papers by Keyword: Hydrothermal

Abstract: WO₃-based composite photocatalysts supported on tungsten disulfide (WS₂), urea, melamine, and graphene nanoplatelets (GNPs) were synthesized and characterized. The SEM micrographs showed that the support materials had a major impact on the composites' shape. While WO₃/WS₂ created layered sheets with scattered nanoparticles, WO₃/melamine and WO₃/urea showed porous and uneven morphologies. Strong interfacial contact was demonstrated by the homogeneous distribution of tiny WO₃ particles on crumpled graphene layers in WO₃/GNPs. W and O from WO₃, as well as S, N, and C elements from the corresponding supports, were verified by EDX. Methyl orange (MO) degradation under light irradiation was used to assess photocatalytic activity. Because of its huge surface area and improved electron mobility, WO₃/GNPs showed the highest degrading efficiency. The WO₃/WS₂ also displayed encouraging activity efficient due to the interfacial charge separation. On the other hand, WO₃/urea and WO₃/melamine performed moderately, most likely as a result of agglomeration and less conductive supports. With WO₃/GNPs emerging as a promising choice for dye degradation and wastewater treatment applications, these findings emphasize the importance of support materials in enhancing WO₃-based photocatalysts.

Abstract: This study developed WO₃/WS₂ composites loaded with noble metals to degrade methyl orange under UV light. Pure WO₃/WS₂ and variations loaded with Au, Ag, Pt, Ru, and Rh were among the photocatalysts. To examine the materials' structural, morphological, and optical characteristics, X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy were used. The highest photocatalytic activity was observed with Au@WO₃/WS₂, degrading MO by 98.59 %. The synergistic interactions between Au nanoparticles and the WO₃/WS₂ heterostructure improved charge separation and light absorption, indicating the composites' potential for effective UV-active photocatalysts for environmental remediation.

Abstract: This study explores the use of biochar derived from Ketapang (Terminalia catappa) leaf waste, prepared via a hydrothermal process and activated with KOH, as an adsorbent for removing mercury (Hg) from aqueous solutions. The study addresses the environmental challenge of heavy metal contamination using a low-cost, sustainable material. Activation increased the surface area of the biochar from 0.067 to 0.450 m²/g, enhancing its adsorption performance. The hydrothermal process was optimized at 220°C, where the biochar exhibited the highest Hg removal efficiency of 71.05% for a 50 ppm Hg(NO₃)₂ solution. The adsorption behavior was best described by the Langmuir isotherm model, indicating monolayer adsorption on a homogeneous surface. The adsorption mechanism likely involves physical and chemisorption interactions, supported by changes in surface morphology, functional groups, and elemental composition. This study demonstrates the promising application of Ketapang leaf biochar as an eco-friendly adsorbent for mercury removal, with implications for water treatment technologies.

Abstract: Nanostructured titanium dioxide (TiO₂) was synthesized via a hydrothermal method to enhance photocatalytic degradation of organic and pharmaceutical contaminants in wastewater. Characterization techniques confirmed the formation of anatase-phase TiO₂ with a tetragonal structure, spherical morphology, and an average crystallite size of 29 nm. The material exhibited a band gap of 3.1 eV. The TiO₂ solution has proven to be very effective in accelerating the breakdown of pharmaceutical and organic contaminants in wastewater, as evidenced by several methods, including high-performance liquid chromatography (HPLC) and Gas chromatography (GC). Photocatalytic performance was evaluated under varying catalyst concentrations and pH levels. Optimal degradation efficiency (72%) was achieved at pH 10, demonstrating TiO₂'s potential as an effective photocatalyst for wastewater treatment.

Abstract: Developing materials for electrodes with engineered interfaces is important for improving supercapacitor performance. Combining metal oxides and two-dimensional (2D) transition-metal dichalcogenides (TMDs) is a promising approach to develop enhanced supercapacitor electrodes. To the best of our knowledge, the electrochemical activity and energy storage of the Fe₃O₄/ReS₂ heterostructure-based electrodes have not been reported in the literature. Therefore, this study employed a two-step hydrothermal method to synthesize a Fe₃O₄/ReS₂ heterostructure and investigated its electrochemical performance. The developed material exhibited exceptional specific capacitance, capacity retention, and high energy and power densities. Moreover, various characterization techniques, including SEM, TEM combined with EDX, and XRD, were employed to examine the surface and structural properties of the produced heterostructures. Electrochemical measurements for supercapacitor application were conducted in 2 M KOH electrolytes for all the developed electrodes. The Fe₃O₄/ReS₂ electrode displayed an excellent energy density of 49.31 Wh/Kg, a power density of 550 W/Kg, a specific capacitance of 322.7 F/g, at a current density of 1A/g, and attained 118 % capacitance retention after 2000 cycles at 10 A/g. A specific capacitance of 789.65 F/g was obtained at 5 mV/s. This work uncovers the potential of Fe₃O₄/ReS₂ heterostructures as promising electrode materials for high-performance energy storage applications.

Abstract: The heterojunction structure Cd(OH)₂/Bi₁₀Cd₃O₂₀ was successfully constructed through a straightforward hydrothermal method. The product was characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), Diffuse reflectance spectrum (DRS), Raman analysis, photocurrent and electrochemical impedance spectroscopy (EIS) measurements. SEM, HRTEM and Raman analysis confirmed that the nanorod Bi₁₀Cd₃O₂₀ was effectively stacked on the surface of the hexagonal microblock Cd(OH)₂, forming the heterojunction composite. This composite demonstrated exceptional photocatalytic performance in the degradation of azo dye pollutants, with a degradation rate for Rhodamine B reaching 98% under optimal synthesis conditions. A plausible photocatalytic mechanism for the heterojunction composite, based on a type I n-n heterojunction, was also proposed. The heterostructure significantly facilitates the migration and separation of charge carriers, thereby enhancing the photoactivity and stability.

Abstract: Barium halide activated with Eu is a typical phosphor material used in imaging plates for computed radiography applications. In this study, BaBrX: Eu (X = Cl, I) was synthesized via the hydrothermal technique. The aim of this study is to further explore the feasibility of the hydrothermal method for synthesizing phosphor materials. This was determined by studying the effect of Eu addition on the structural and optical properties of BaBrX (X = Cl, I). X-ray diffraction (XRD) was employed to determine the crystallinity of the prepared samples, while optical properties were observed using photoluminescence (PL) spectroscopy. The sharp, narrow, and high-intensity peaks of XRD diffractogram indicated that all samples exhibited good crystallinity. The addition of the Eu element as an activator resulted in a blue-shift with broad and higher intensity of the main emission peak for several samples. This study demonstrates that the addition of the Eu element to the host materials has altered the structural properties and improved the optical properties of the prepared samples, significantly demonstrating the feasibility of the hydrothermal method for synthesizing phosphor materials.

Abstract: TiO₂ nanomaterial is a semiconductor material that exhibits promising photocatalysis activity. TiO₂ nanomaterials can be converted into several forms, including TiO₂ nanotubes, which have a larger surface area and more applications. In this study, TiO₂ nanotubes were synthesized hydrothermally using TiO₂ micro powder precursors. The synthesis involved two hydrothermal stages: the first to synthesize TiO₂ nanoparticles from TiO₂ micro powder precursors, and the second to synthesize TiO₂ nanotubes from TiO₂ nanoparticle precursors. TiO₂ micro powder was added to the synthesis of TiO₂ nanoparticles by hydrothermal at mole ratios of TiO₂/NaOH of 0.01, 0.025, and 0.04, respectively. The TiO₂ nanoparticles obtained exhibit a morphology in the form of short fibers, with particle sizes increasing as the mole ratios are added. Furthermore, they possess an anatase crystal structure at all mole ratios of TiO2/NaOH. Subsequently, the TiO₂ nanoparticles are calcined at 450°C. The results of the TiO2 nanoparticle calcination show that the morphology is in the form of short fibers, which are smaller than those of the uncalcinated sample. The calcinated sample also has larger particle sizes and an anatase crystal structure, compared to the uncalcinated sample. The TiO₂ nanotubes obtained exhibit an elongated tube morphology with outer diameters ranging from 3.93 to 11.44 nm, inner diameters ranging from 2.5 to 4.25 nm, and a wall thickness of 1.09 to 3.4 nm. The surface area of the TiO2 nanotubes is 256.744 m²/g.

Abstract: The current work concerns preparing cobalt manganese ferrite (Co_0.2Mn_0.8Fe₂O₄) and decorating it with polyaniline (PAni) for supercapacitor applications. The X-ray diffraction findings (XRD) manifested a broad peak of PAni and a cubic structure of cobalt manganese ferrite with crystal sizes between 21 nm. The pictures were taken with a field emission scanning electron microscope (FE-SEM), which evidenced that the PAni has nanofibers (NF_s) structures, grain size 33 – 55 nm, according to the method of preparation, where the hydrothermal method was used. The magnetic measurements (VSM) that were conducted at room temperature showed that the samples had definite magnetic properties. Additionally, it was noted that the saturation magnetization value of PAni/Co_0.2Mn_0.8Fe₂O₄ nanocomposite and Co_0.2Mn_0.8Fe₂O₄ nanoparticles are maximum saturation magnetization values of (4.7) and (9) emu g⁻¹ respectively. Studying properties of electrochemical which were tested in 1 M of H₂SO₄ by using the CV cyclic voltammetry analysis, galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS), found the highest capacitance is 596 F/g.

Abstract: Hydroxyapatite Carbonate (CHA) is a material that is found to have a composition more similar to bone, with a higher bioactivity than Hydroxyapatite (HA). CHA was synthesized using precipitation and hydrothermal methods using (NH₄)₂HPO₄ as a phosphate source, NH₄HCO₃ as a carbonate source, and Pokea shells as a calcium source. In this study, the Pokea shells were crushed, calcined, and characterized based on physicochemical tests. CaO from Pokea shell contains 74.33% calcium. CHA was successfully produced by precipitation method at room temperature and hydrothermal at 120 C for 8 h. Sample characterization was carried out using X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Scanning Electron Microscope Energy Dispersive X-Ray Spectroscopy (SEM-EDX). Based on XRD data, there are differences in the crystal size of CHA produced via precipitation and hydrothermal methods, where the crystal sizes of Precipitation CHA-1 and Hydrothermal CHA-2 are 6.388 nm and 25.969 nm. The FTIR results of both CHA show the functional groups typical of CHA, namely OH-, CO, CaO, PO₄^3-, and CO₃^2-. From the Ca/P EDX data results, Precipitation CHA-1 and Hydrothermal CHA-2 do not differ much, namely 1.71 and 1.69, and this value indicates that CHA has been formed.